Once a crop has been harvested, residual crop materials frequently remain on the farmland surface. Typically, these residual crop materials are incorporated within the soil profile of the farmland in an effort to maintain soil nutrient integrity. For example, management of corn cropped fields commonly includes the incorporation of the residual corn stalks with field soil once the corn, and occasionally a portion of the stalk, has been harvested. Whereas some growers harvest a majority of the kernel, cob, and stalk material, others harvest only the kernel and discharge a majority of the chaff or cob and stalk materials onto the farmland. Regardless of the quantity of stalk material that is harvested, the subsequent preparation of the farmland requires incorporation of the stalk or crop residue with the field soil. It is generally understood that the size of the crop residue particles as well as the surface area of the crop residue exposed to the soil affects crop residue decomposition. Specifically, reduced crop residue particle size and increased surface contact of the crop residue with adjoining soil improves crop residue decomposition.
Frequently, a crop residue conditioner, such as a stalk chopper, is pulled across the harvested field during autumn. The stalk chopper cuts the remaining stalks into smaller, more easily workable and degradable sized pieces. Thereafter, a disc harrow is used to smooth and level the farmland or seedbed and till a portion of the crop residue with the soil. The disc harrow not only mixes the crop residue with the underlying soil to return nutrients to the soil but also can be used to establish a residue layer over the farmland to protect against erosion and provide moisture control during the winter months before replanting in the spring.
Disc harrows include one or more disc gangs, each including a series of steel discs or reels with tapered or beveled peripheral edges. The discs, although tending to roll or rotate as they are pulled forward, penetrate into and break up the soil and stalks and other crop residue. The soil and crop residue then ride along and across the concave surfaces so as to be turned or inverted. A portion of the residue is buried with this turning, with the percentage of buried residue increasing with the amount of soil turning. The amount of crop residue that is retained on the seedbed surface may also be controlled by setting the angle of attack or “gang angle”, such as described in U.S. Pat. No. 6,612,381, the disclosure of which is incorporated herein by reference.
During harrowing of the farmland the disc harrow may encounter various obstructions, such as rocks, stumps, and roots. To reduce the impact of such obstructions and thereby potential damage to the disc harrow, the disc gangs are often resiliently supported on the harrow mainframe so that each gang can independently yield to the obstructions. Conventionally, the reels are mounted to a shaft or axle which is then mounted to the harrow mainframe via U-shaped or C-shaped spring members, also referred to as shanks or cushions. These spring members are designed to absorb the blunt forced placed on the disc gangs when the reels meet with an obstruction. However, these spring members are typically coupled to the mainframe and the gang shaft in a fixed connection, as illustrated in U.S. Pat. No. 4,066,132 to Rehn, U.S. Pat. No. 4,404,372 to Rozeboom, and U.S. Pat. No. 7,131,501 to Svendsen et al. As a result, when an obstruction is encountered during harrowing the springs will deflect to absorb some the impact of the obstruction, but the obstruction remains in the path of the harrow until forcibly cleared by the rotating reels or forcibly pulled over the obstruction by the tractor or other towing means. Moreover, once the spring has fully deflected, it cannot absorb any additional force placed on the disc gangs. As such, while such cushions have reduced wear to the disc gangs, their effectiveness is limited when larger farmland obstructions are encountered.
Thus, there remains a need for a farm implement having a shock absorbing assembly that not only absorbs the impact of an obstruction during the harrowing process, but also places less stress on the farm implement during clearing of the obstruction.